Turning method for a cnc-lathe and a turning tool

ABSTRACT

A turning method for a computerized numerical control lathe includes providing a turning tool having a cutting portion, the cutting portion including a first nose portion, the first nose portion including a first cutting edge, a second cutting edge, and a convex nose cutting edge connecting the first and second cutting edges, wherein the first and second cutting edges are straight or substantially straight in a top view. The method further includes providing a metal work piece, rotating the metal work piece around a work piece rotational axis, and making a first pass where the first cutting edge is active and the second cutting edge is inactive. A first machined surface is generated by the convex nose cutting edge, and during at least a portion of the first pass, an entering angle and an angle, which the first cutting edge forms with the work piece rotational axis, simultaneously varies.

TECHNICAL FIELD OF THE INVENTION

The present invention belongs to the technical field of metal cutting.More specifically the present invention belongs to the field of turningof a metal work piece, by use of computer or computerized numericalcontrol, i.e. CNC, machines. More specifically, the present inventionrelates to turning method, an automated computer-implemented method, anda turning tool.

BACKGROUND OF THE INVENTION AND PRIOR ART

In turning of metal work pieces using a CNC-lathe, many methods ofturning are known. Conventionally, the orientation of the turning toolin relation to the work piece is constant during machining and a turningoperation is performed in two linear axes. The entering angle, alsoknown as setting angle, can conventionally not be chosen by other meansthan by changing the turning tool.

U.S. Pat. No. 6,715,386 B2 describe a method where various settingangles of a cutting insert can be carried out. As shown in FIG. 10,turning (i.e. rotation) of the cutting insert is made between a firstmachining sequence and a second machining sequence.

The inventors have found that a method for turning can be furtherimproved. Especially, the inventors have found that there is a need toimprove tool life and/or chip control.

SUMMARY OF THE INVENTION

The inventor has found that there is a need for an improved method forimproving tool life and/or chip control. Especially, the inventors havefound that there is a need for an improved method when machining apredefined feature having a complicated shape, especially an externalgroove. In such a case, the inventors have found that it is advantageousto vary the entering angle for reducing the risk of interference betweeninactive parts of the turning tool and the metal work piece, and/orimproving chip control and/or tool life. The inventors have furtherfound that there is a need for a turning method which reduces the riskof vibrations. The inventors have further found there is a need for aturning method which maximizes the cutting time of a CNC-lathe, therebyreducing the manufacturing cost. By such a turning method, the tool lifecan be increased because the risk of rapid changes in cutting force,e.g. from rapid changes in cutting depth, may be reduced. By such aturning method, a component or a feature of a component having acomplicated shape, such as a groove, can be machined using a singleturning tool, thereby reducing the machining time.

This aim is at least to some extent achieved by a turning method for acomputerized numerical control lathe comprising the steps of: providinga turning tool comprising a cutting portion, the cutting portioncomprising a first nose portion, the first nose portion comprising afirst cutting edge, a second cutting edge, and a convex nose cuttingedge connecting the first and second cutting edges, wherein the firstand second cutting edges are straight or substantially straight in a topview; providing a metal work piece; rotating the metal work piece arounda work piece rotational axis; making a first pass such that the firstcutting edge is active and such that the second cutting edge isinactive, such that a first machined surface is generated by the convexnose cutting edge, and such that during at least a portion of the firstpass, an entering angle and an angle which the first cutting edge formsin relation to the work piece rotational axis simultaneously varies.

Said method is thus a turning method, preferably an external turningmethod, where a rotationally symmetrical surface is formed. Said methodis for a computerized numerical control (CNC) lathe. A turning tool isprovided. The turning tool comprises a cutting portion, preferably inthe form of a cutting insert in the form of a turning insert. Thecutting portion comprises a first nose portion. Preferably, the cuttingportion comprises a second nose portion. The first nose portioncomprises a first cutting edge, a second cutting edge, and a convex nosecutting edge connecting the first and second cutting edges, wherein thefirst, second and nose cutting edges connects a top surface and a sidesurface. Said top surface is arranged to function as a rake face. Saidtop surface preferably comprises chip breaking means, preferably in theform of one or more protrusions and/or depressions. The first and secondcutting edges are straight or substantially straight or linear in a topview. A metal work piece is provided which preferably is rotationalsymmetric or substantially rotational symmetric. The metal work piece isclamped to the CNC-lathe by clamping means, such as clamping jaws. Themetal work piece may be clamped at one end or at opposite ends.

The metal work piece is rotated around a work piece rotational axisthereof. Preferably, the metal work piece is rotated in exactly onedirection around the work piece rotational axis.

The first cutting edge is preferably active, i.e. in cut, during theentire time of cut during the first pass.

A pass can be understood as a turning sequence, which chronically can bedefined as the time between going into cut and going out of cut, i.e. atime span during which chips are removed from the metal work piece. Saidpass can further geometrically or spatially be defined as how theturning, more specifically the cutting portion of the turning tool,moves in relation to the metal work piece, from going into cut untilgoing out of cut.

The expression “the first cutting edge is active and such that thesecond cutting edge is inactive” may alternatively be formulated as “thefirst cutting edge is ahead of the second cutting edge during the firstpass”.

During the first pass, or at least during a portion of the first pass,the first cutting edge is active, i.e. cutting metal, and the secondcutting edge is inactive, i.e. not cutting metal. A first machinedsurface is generated by the convex nose cutting edge. During at least aportion of the first pass, an entering angle and an angle which thefirst cutting edge forms in relation to the work piece rotational axissimultaneously, i.e. synchronically, varies or changes.

In other words, the entering angle varies or changes, and the anglewhich the first cutting edge forms in relation to the work piecerotational axis varies or changes.

The entering angle is defined as the angle between the first cuttingedge and the direction of movement of the surface generating point ofthe nose cutting edge.

The entering angle is preferably 5-140°, even more preferably 20-110°.

The entering angle may be constant at one or more portions during thefirst pass.

The angle which the first cutting edge forms in relation to the workpiece rotational axis is preferably varies simultaneously as theentering angle varies during the first pass. In other words, said anglespreferably varies synchronically during the first pass.

The variation or altering of said angles may be achieved by a rotationor movement of the work piece rotational axis. Alternatively, andpreferably, the variation of said angles are achieved by a rotation ormovement of the turning tool around a tool rotational axis. Said toolrotational axis preferably is normal or substantially normal to a planecomprising a top surface or rake face of the cutting portion. Said topsurface or rake face is preferably not planar, however a plane may bedefined which substantially comprises the top surface or rake face.

The first pass is defined as from going into cut until going out of cut,preferably from where the nose cutting edge goes into cut to where thenose cutting edge goes out of cut. The location on the metal work piecefor going into cut is spaced apart from the location for going out ofcut.

The cutting depth during the first pass may be constant. Alternatively,the cutting depth may vary during the first pass.

During the first pass, a cutting speed is preferably constant orsubstantially constant. Said cutting speed is preferably 40-1500 m/min,even more preferably 50-300 m/min.

The first pass preferably starts with an increasing cutting depth, andpreferably ends with a decreasing cutting depth. Preferably, a cuttingdepth at an intermediate portion of the first pass is preferablyconstant, preferably 0.2-15 mm, even more preferably 0.4-4 mm. Saidintermediate portion is preferably 50-99% of the first passchronologically.

According to an embodiment, the first pass is a non-linear first pass.

By such a method, a feature having a complex shape can be machined in ashorter time.

The method comprises the step of making a non-linear first pass or toolpath. Non-linear means that the machined surface generated from thefirst pass is not completely cylindrical, conical or flat.

That the first pass is non-linear means that the generated surface isnon-cylindrical and/or non-conical and/or non-planar. The generatedsurface may e.g. comprise a combination or set of sub-surfaces such as acylindrical surface and/or a planar surface and/or a concave surfaceand/or a convex surface. Preferably, the generated surface comprises acylindrical surface, concentric with the rotational axis of the metalwork piece, and a concave surface. In other words, the non-linear firstpass preferably comprises a linear portion, e.g. a portion where acylindrical surface is generated, and a curved portion, e.g. a portionwhere a concave surface is generated.

The first cutting edge is preferably active, i.e. in cut, during theentire time of cut during the non-linear first pass.

According to an embodiment, the method comprises the further step ofduring at least a portion of the first pass increasing the enteringangle and reducing a surface generating feed rate.

By such a turning method, the risk of interference or crash is reduced.In other words, the risk of contact between a non-cutting portion of theturning tool and the metal work piece is reduced. By such a turningmethod, a more complicated shape may be machined.

By such a turning method, the chip control is further improved because arelatively low entering angle at a relatively early stage of the cutgive a chip direction which is relatively more directed away from therotational axis of the metal work piece, which may be an advantage whenmachining a complex shape such as an external groove.

By such a turning method, the tool life can be improved. This is becausethat the maximum chip thickness varies less than if the surfacegenerating feed would be constant. A further aspect is that theinventors have found that a relatively low entering angle isadvantageous for tool life, and high entering angle is advantageous atleast generally with respect of reducing the collision risk, and thecollision risk generally increases as the pass progresses. Thus, by sucha turning method, the risk of interference or crash is reduced. In otherwords, the risk of contact between a non-cutting portion of the turningtool and the metal work piece is reduced. By such a turning method, amore complicated shape may be machined.

The surface generating feed rate is a velocity. The surface generatingfeed rate may preferably be 0.05-1.2 mm per revolution. The surfacegenerating point of the nose cutting edge preferably moves along thenose cutting edge. However, this effect is normally small.

When the entering angle varies, the distance which a surface generatingpoint of the nose cutting edge moves per revolution can be designated asthe surface generating feed rate and can be found as the distance whichthe surface generating point of the nose cutting edge moves perrevolution of the metal work piece.

The machined surface has a shape and/or structure which is wave-shaped.The distance between adjacent tops or cusps is equal to the surfacegenerating feed rate.

The result of such a method can e.g. be seen on a machined component,where a distance between feed marks, such as cusps, is smaller at theend of the pass or is decreasing towards the end of the pass.

During at least a portion of the first pass, the entering anglepreferably increases simultaneously, i.e. synchronically, as thevelocity of the nose cutting edge, or more precisely a surfacegenerating point of the nose cutting edge, is decreased. In other words,preferably the entering angle increases simultaneously as the surfacegenerating feed rate decreases.

Alternatively, the entering angle may increase incrementally, such asincreasing in steps of a fixed value, such as in steps of 1° or 2°simultaneously as the feed rate decrease incrementally, such asdecreasing in steps of a fixed value or multiples of a fixed value, suchas in steps of e.g. 0.001 or 0.005 mm per revolution.

According to an embodiment, the entering angle and the angle which thefirst cutting edge forms in relation to the work piece rotational axiscontinuously varies.

By such a smooth or step-less or seam-less variation of said angles, theinventors have found that the machined surface quality is improved.

The entering angle continuously, i.e. uninterruptedly or gradually,varies or changes.

The angle which the first cutting edge forms in relation to the workpiece rotational axis continuously, i.e. uninterruptedly or gradually,varies or changes.

According to an embodiment, the entering angle and the angle which thefirst cutting edge forms in relation to the work piece rotational axisvaries by a rotation of the turning tool around a tool rotational axis,wherein the tool rotational axis is perpendicular to or substantiallyperpendicular to the work piece rotational axis.

By such a turning method, where the tool rotational axis isperpendicular to the work piece rotational axis, the variation of saidangles may be achieved by a variation of the same amount of the machinespindle, to which machine spindle said turning tool is connected.

The expression “substantially perpendicular” means that the toolrotational axis is within 15° from being perpendicular to the work piecerotational axis.

Preferably, the turning tool is elongated along the tool rotationalaxis. In other words, the turning tool is more elongated along the toolrotational axis that along axes perpendicular to the tool rotationalaxis.

Preferably, a top surface of the cutting portion, the top surface beingconnected to the first, second and nose cutting edges, is arranged in aplane perpendicular to or substantially perpendicular to the toolrotational axis. Said top surface is facing away from the couplingportion of the turning tool.

By such a method, the risk for vibrations is reduced.

Preferably, the rotation of the turning tool around a tool rotationalaxis during the first pass is in one direction only, i.e. clock-wiseonly or anti clock-wise only.

If the turning method comprises a second pass, such as a non-linearsecond pass, the rotation of the turning tool around a tool rotationalaxis is preferably in the opposite direction in relation to thedirection of rotation during the first pass.

Regarding the metal work piece, the direction of rotation around saidwork piece rotational axis is the same during both the first and secondpasses.

Preferably, the rotation of the turning tool around a tool rotationalaxis during the first pass is 50-200°, even more preferably 70-160°.

According to an embodiment, the method comprises the further step ofduring at least a portion of the first pass moving the tool rotationalaxis in relation to the work piece rotational axis.

By such a turning method, the turning method can be performed in aneasier manner, compared to if the tool rotational axis and/or metalworkpiece was moving.

In other words, the movement of the turning tool in relation to themetal work piece includes a movement of the tool rotational axis inrelation to the work piece rotational axis. Said movement of the toolrotational axis is preferably a parallel movement. Said movementpreferably includes a non-linear movement. The work piece rotationalaxis is not moving.

According to an embodiment, the method comprises the further step ofduring at least a portion of the first pass moving the turning tooltowards the work piece rotational axis.

By such a turning method, the first machined surface is an externalsurface, which may comprise an internal corner and/or a groove and/or apocket and/or a concavity.

Said internal corner is less than 180°, preferably 90°+/−10°. A 90°internal corner comprises a cylindrical or conical first surface and aflat or conical second surface, where the second surface is a radiallyouter surface and where the first surface and the second surface areconnected. Radially outer means radially outer in relation to the workpiece rotational axis, i.e. at a greater distance from the work piecerotational axis. Said first and second surface are preferably connectedby a concave surface. Preferably, said internal corner comprises acylindrical first surface and a flat second surface, where said firstand second surfaces are connected by a concave surface, and where saidsecond surface is a radially outer surface.

According to an embodiment, the entering angle and the angle which thefirst cutting edge forms in relation to the work piece rotational axisvaries during a non-linear portion of the non-linear first pass.

In other words, both of said angles varies during at least a portion ofa non-linear portion, such as a curved segment, of the non-linear firstpass.

According to an embodiment, the method comprises the further step ofsetting a maximum chip thickness to a constant predetermined value or tobe within a predetermined range during at least a portion of the firstpass.

By such a turning method, the tool life and/or chip control is furtherimproved.

The result of such a method can e.g. be seen on a machined component,where a distance between feed marks, such as cusps, is smaller at theend of the pass or is decreasing towards the end of the pass.

The maximum chip thickness h_(x), also known as undeformed chipthickness, sometimes called “hex”, is the maximum chip thicknessmeasured in a direction perpendicular to the chip generating firstcutting edge, if the second cutting edge is inactive. If the secondcutting edge is active and the first cutting edge is inactive, themaximum chip thickness is measured perpendicular to the chip generatingsecond cutting edge. In turning, where the entering angle and the feedrate are constant and where the cutting depth is above the nose cuttingedge, the chip thickness h_(x) is constant and defined as f x sin K,where f is the feed rate per revolution and K is the entering angle. Forexample, at a 90° entering angle, the chip thickness, or maximum chipthickness, is equal to the feed rate. In this present case though, theentering angle may vary, and the feed rate may vary along the firstcutting edge.

When the entering angle K varies, the maximum chip thickness h_(x) isthe maximum chip thickness measured along a line perpendicular to thefirst cutting edge.

When the entering angle K varies, the distance which the surfacegenerating point of the nose cutting edge moves per revolution can bedesignated as the feed rate per revolution. Said feed rate perrevolution in this case, when the entering angle K varies, can bedesignated as the surface generating feed rate, and can be fined as thedistance which the surface generating point of the nose cutting edgemoves per revolution of the metal work piece.

“Substantially constant maximum chip thickness” means that the maximumchip thickness h_(x) varies within +/−25% during at least 90% of thefirst and/or second pass. The entering angle K is defined as the anglebetween the surface generating feed direction and the active maincutting edge, i.e. the first cutting edge, or the second cutting edge.During the first pass, the first cutting edge is the active main cuttingedge. During the second pass, the second cutting edge is the maincutting edge. Said entering angle K is preferably less than or equal to130°, preferably 5°-110°.

Said predetermined value or predetermined range may preferably beautomatically selected from an electronic database or an electroniclibrary. Preferably, said predetermined value or predetermined range isequal to or substantially equal a feed recommendation from themanufacturer of the cutting portion, preferably with the material of themetal work piece taken into account.

Preferably, the maximum chip thickness h_(x) is 0.01-3 mm, morepreferably 0.03-2 mm, even more preferably 0.04-1.2 mm.

According to an embodiment, the first non-linear pass includes machiningof a bottom surface of an external groove,

wherein the groove is limited by a first side wall, a second side wall,the bottom surface, a first corner surface and a second corner surface,

wherein the first corner surface is connecting the bottom surface andthe first side wall,

wherein the second corner surface is connecting the bottom surface andthe second side wall,

wherein the method comprises the steps of moving the nose cutting edgetowards the first corner surface; and

increasing a speed of rotation of the turning tool around the toolrotational axis as a portion of the turning tool, spaced apart from thefirst cutting insert, reaches a predetermined distance from the firstside wall.

The first non-linear pass thus includes machining of a bottom surface,and preferably a first corner surface of an external groove. The bottomsurface is preferably a cylindrical surface concentric with the workpiece rotational axis.

In other words, the first machined surface includes the bottom surfaceof the groove.

The groove, or pocket, is an external groove. The groove preferablyopens in a direction away from the work piece rotational axis.Alternatively, the groove opens in a direction which is parallel to orsubstantially parallel to the work piece rotational axis.

The groove is limited by a first side wall, i.e. a first side wallsurface, and a second side wall, i.e. a second side wall surface, whicheach preferably are perpendicular to or substantially to the work piecerotational axis. The first side wall is facing the second side wall.

The groove is further limited by a first corner surface and a secondcorner surface, where said corner surfaces are concave surfaces.

The method comprises the steps of generating a portion of the firstmachined surface, i.e. at least a portion of the bottom surface, bymoving the surface generating nose cutting edge towards the first cornersurface; and increasing a speed of rotation of the turning tool aroundthe tool rotational axis as a portion of the turning tool, wherein saidportion is inside the groove and spaced apart from the first cuttinginsert, reaches a predetermined distance, measured parallel to the workpiece rotational axis, from the first side wall.

Increasing the speed of rotation of the turning tool around the toolrotational axis can alternatively be understood as increasing the speedof entering angle increase. In other words, the increase rate of theentering angle is not constant as said portion of the turning toolreaches said predetermined distance from the first side wall.

In other words, said portion of the turning tool reached saidpredetermined distance from the first side wall prior to the surfacegenerating nose cutting edge.

The predetermined distance is preferably 1-30 mm, even more preferably2-15 mm.

Said portion of the turning tool is preferably either a front end of thetool body, or a second cutting insert connected to said front end of thetool body.

According to an embodiment, the method comprises the further step ofduring at least a portion of the first pass setting a chip area to bebelow a predetermined value or to be within a predetermined range.

By such a turning method, the tool life may be improved.

The normal definition of chip area is depth of cut (also known ascutting depth) x feed per revolution. The revolution is related to thework piece. In other words, the chip area is the area of materialremoved per revolution. More specifically, the feed per revolution isdefined as the distance which the surface generating point of the nosecutting edge travels per revolution.

According to an embodiment, the method comprises the further step ofsetting the maximum chip width to a predetermined value or to apredetermined range during at least a portion of the first pass.

By such a turning method, the tool life may be improved.

The term setting the maximum chip width means to select a predeterminedpoint or range along the first cutting edge which is active during thefirst pass. In other words, a portion of the first cutting edge isinactive. The maximum chip width is preferably less than or equal to 12mm, even more preferably less than or equal to 6 mm, even morepreferably less than or equal to 3 mm. The maximum chip width ispreferably more than or equal to 0.2 mm, more preferably more than orequal to 0.5 mm.

Preferably, the maximum width varies within +/−40%, even more preferablywithin +/−20%, from a predetermined value.

Alternatively, formulated, the method comprises the step of setting thecutting depth to be a predetermined value or to be within apredetermined range.

According to an embodiment, the method comprises the further step ofmaking a second pass such that the second cutting edge is active andsuch that the first cutting edge is inactive,

wherein at least a portion of the first machined surface is machinedduring the second pass, thereby generating a second machined surface bythe convex nose cutting edge.

By such a turning method, the machining time can be reduced especiallywhen e.g. a pocket or a groove is to be machined and where a large depthof material needs to be removed.

Preferably, the direction of rotation of the metal work piece aroundsaid work piece rotational axis is the same during both the first andsecond passes.

Preferably, a direction of the second pass is opposite to orsubstantially opposite to the first pass.

According to an embodiment, the cutting portion is in the form of acutting insert,

wherein the cutting insert comprises a top surface,

wherein in a top view an angle between the first cutting edge and asecond cutting edge is less than 90°,

and wherein in a top view, the convex nose cutting edge has a radius ofcurvature which is 0.15-1.3 mm,

wherein the turning tool comprises a tool body,

wherein the tool body comprises a coupling portion, an intermediateportion, and an insert seat,

wherein the intermediate portion extending along a longitudinal centeraxis thereof,

wherein the cutting insert is mounted in the insert seat,

wherein the tool body extends between the coupling portion and a frontend of the tool body,

wherein the front end of the tool body comprises the insert seat,

wherein the top surface of the cutting insert is facing away from thecoupling portion,

wherein a longitudinal center axis of the coupling portion defines atool rotational axis,

wherein the entering angle and the angle which the first cutting edgeforms in relation to the work piece rotational axis varies during thefirst pass as a result of a rotation of the turning tool around the toolrotational axis.

By such a method, the risk for vibrations is further reduced, becausecutting forces are directed towards the coupling forces to a greaterextent. The angle between the first cutting edge and a second cuttingedge is preferably 10-80°, even more preferably 10-65°. By such aturning tool, more complex shapes can be machined, compared to if saidangle would be greater than 80°.

In a top view, the cutting insert is preferably completely inside anouter peripheral surface of the coupling portion.

According to an embodiment, in a top view, the intermediate portion isat least 50% more elongated along a bisector formed between the firstand second cutting edges than along a line which is perpendicular to thebisector and intersecting the longitudinal center axis of theintermediate portion.

Formulated differently, the front end of the tool body is at least 50%more elongated along a bisector formed between the first and secondcutting edges than along a line which is perpendicular to the bisectorand intersecting the longitudinal center axis of the intermediateportion.

According to an embodiment, a computer program has instructions whichwhen executed by a computer numerical control lathe cause the computernumerical control lathe to perform the above described method.

Said computer program, or computer program product, thus controls thetool path of the turning tool, the cutting data and the rotation of themetal work piece.

By such a computer program, said turning method can be easilyimplemented on numerous CNC-lathes or CNC-machines.

Said computer program have instructions for controlling movement androtation of the turning tool, and instructions for rotation of the metalwork piece, for removing stock by means of a turning operation accordingto the above defined method.

Said instructions may include cutting data such as cutting speed, feedrate, tool path and cutting depth.

A computer readable medium may have stored thereon said computerprogram.

A data stream may be representative of said computer program.

According to an aspect of the invention, an automatedcomputer-implemented method for generating commands for controlling acomputer numerically controlled machine to fabricate a feature from ametal workpiece rotatable around a work piece rotational axis thereof bymeans of any of the above described turning tools,

wherein the method comprises the step of configuring a first passaccording to any of the above described first passes.

According to an aspect of the invention, an automatedcomputer-implemented method for generating commands for controlling acomputer numerically controlled machine to fabricate a feature from ametal workpiece rotatable around a work piece rotational axis thereof bymeans of a turning tool,

wherein the turning tool comprises a cutting portion, the cuttingportion comprises a first nose portion, the first nose portion comprisesa first cutting edge, a second cutting edge, and a convex nose cuttingedge connecting the first and second cutting edges, wherein the firstand second cutting edges are straight or substantially straight in a topview,

wherein the method comprises the step of:

configuring a first pass such that the first cutting edge is active andsuch that the second cutting edge is inactive, such that a firstmachined surface is generated by the convex nose cutting edge, and suchthat during at least a portion of the first pass, an entering angle andan angle which the first cutting edge forms in relation to the workpiece rotational axis simultaneously varies.

Preferably, a tool path designer, using the automated computerimplemented method for generating commands for controlling a computernumerical controlled machine, accesses a CAD drawing of the feature in astandard CAD format. The tool path designer selects the turning tool tobe used in fabrication of the feature from a menu. The tool pathdesigner defines the properties of the turning tool, e.g. by collectingthe characteristics of the turning tool from an electronic tool libraryor by other means. Said tool characteristics include the geometry orouter boundary lines of the turning tool and cutting datarecommendations. For the sake of simplicity, the illustrated feature ischosen to be a feature, e.g. an external groove, that can be fabricatedby a single machining function. It is appreciated that the applicabilityof the present invention is not limited to features which can befabricated by a single machining function.

The tool path designer then defines the geometry of the metal work pieceto be used in fabrication of the feature. This may be done automaticallyby the automated computer implemented apparatus of the present inventionor manually by the tool path designer. The tool path designer thenspecifies the specific metal material of the metal work piece. A set ofmachining steps or passes may be calculated recursively, wherebypreferably initially a first pass is calculated for an initial region ofthe workpiece, and thereafter a subsequent second pass is similarlycalculated for a remaining region of the workpiece. Said first andsecond passes are preferably non-linear. Additional subsequentsequential machining steps or passes may be similarly calculated, untila tool path for machining the desired feature has been calculated.

The automated computer-implemented method may preferably be used incomputer aided manufacturing. The method preferably takes into accountconstraints such as the shape of the feature and the shape of theturning tool. The method preferably includes the constraint ofminimizing the risk of collision between the metal work piece and theturning tool. The automated computer-implemented method can preferablybe used for any of the above described turning method embodiments orparts thereof.

The automated computer-implemented method preferably comprises thefurther step of during at least a portion of the first pass increasingthe entering angle and reducing a surface generating feed rate,preferably simultaneously.

According to an embodiment, the automated computer-implemented methodcomprises the further step of setting a maximum chip thickness to aconstant predetermined value or to be within a predetermined rangeduring at least a portion of the first pass.

Preferably, said value or range of the maximum chip thickness is chosenfrom an electronic tool library or an electronic machining database,which preferably includes the material and shape of the cutting portion(preferably in the form of a cutting insert) and recommended cuttingdata for such cutting portion for at least one specific type of metal.The maximum chip thickness is in other words selected as a result of atleast the metal work piece material and/or the material and/or shape ofthe cutting portion.

The tool path designer preferably sets a first entering angle, relatedto a first point of the first pass, and a second entering angle, relatedto a second point of the first pass, whereby the automatedcomputer-implemented method preferably comprises the further steps of:

calculating the surface generating feed rate of feed rate, according tothe formula f=maximum chip thickness/sin K, for the first and secondpoints; and linearly interpolating the feed rate (or surface generatingfeed rate) and entering angle for each point along the machined surfacebetween said first point and said second point.

According to an embodiment, the feature is in the form of an externalgroove limited by a bottom surface, first and second side walls, andfirst and second corner surfaces,

wherein the first corner surface connects the bottom surface and thefirst side wall,

wherein the second corner surface connects the bottom surface and thesecond side wall,

wherein the first pass includes the machining of the bottom surface andthe second corner surface,

wherein the method comprises the further steps of setting a cornerentering angle, a corner exit entering angle, and a longitudinal exitentering angle,

and step-less or incrementally vary the entering angle between thecorner entering angle and the corner exit entering angle, and betweenthe corner entering angle and the longitudinal exit entering angle.

The bottom surface is preferably a cylindrical surface concentric withthe rotational axis of the metal work piece. The first and second sidewalls are preferably flat or substantially flat and perpendicular to therotational axis of the metal work piece. The first and second cornersurfaces are preferably curved, preferably having a constant radius ofcurvature.

The first pass is non-linear and includes the machining of the bottomsurface and the second corner surface, preferably also the first cornersurface.

The non-linear first pass comprises the machining of the second cornersurface in a curved direction towards the rotational axis and towardsthe bottom surface, followed by the machining of the bottom surface in adirection away from the second corner surface.

The corner entering angle is the entering angle at the start or entry ofthe machining of the second corner surface. The corner exit enteringangle is the entering angle at the end or exit of the second cornersurface. The corner exit entering angle is equal to a longitudinalentering angle. The longitudinal exit entering angle is the enteringangle at the start or entry of the machining of the bottom surface.

Preferably, the corner entering angle is greater than the corner exitentering angle.

Preferably, the longitudinal exit entering angle is greater than thecorner exit entering angle.

Preferably, the corner entering angle is set to 60-120°, even morepreferably 80-110°.

Preferably, the corner exit entering angle is set to 20-80°, even morepreferably 25-45°.

Preferably, the longitudinal exit entering angle is set to 60-120°, evenmore preferably 80-110°.

Preferably, the non-linear first pass includes the machining of thefirst corner surface, which is made immediately after the machining ofthe bottom surface.

The entering angle at the start or entry of the machining of the firstcorner surface is equal to the longitudinal exit entering angle.

The entering angle at the end or exit of the first corner surface isdesignated K₆, and is preferably set to 10-80°, even more preferably25-45°.

The non-linear first pass may be such that the nose cutting edge goesinto cut prior to the second corner surface. In such a case, an entryentering angle is designated K₁.

All entering angles are defined as the angle between the first cuttingedge and the surface generating feed direction.

The first cutting edge is active at least during the machining of thebottom surface. Even if the first cutting edge is inactive during aportion of the non-linear first pass, an entering angle may still bedefined following the above definition.

The entering angle K is preferably varied continuously, i.e. withoutsteps, during at least a portion of the non-linear first pass.Alternatively, the entering angle K is incrementally varied, preferablyin steps of less than 2°. The CNC-lathe sets the limit for variation ofthe entering angle. Preferably, the automated computer-implementedmethod comprises a second non-linear pass, where the first cornersurface is machined prior to the bottom surface, and where the bottomsurface is machined prior to the second corner surface.

In other words, the non-linear second pass is generally in an oppositedirection to the non-linear first pass.

During the second non-linear pass, entering angles are preferablyselected in a corresponding manner as for the non-linear first pass.Preferably, the automated computer-implemented method comprises asequence where the non-linear passes are alternated.

According to an aspect, a turning tool comprises a tool body and acutting portion, wherein the cutting portion comprises a first cuttinginsert and a second cutting insert,

wherein the tool body comprises a coupling portion, an intermediateportion, a first insert seat for the first cutting insert and a secondinsert seat for the second cutting insert,

wherein the tool body extends between the coupling portion and a frontend of the tool body,

wherein the front end of the tool body comprises the first insert seatand the second insert seat,

wherein the first cutting insert comprises a bottom surface opposite atop surface, wherein a side surface connects the top and bottomsurfaces,

wherein a mid-plane extends mid-way between the top and bottom surfaces,

wherein the top surface of the first cutting insert is facing away fromthe coupling portion,

wherein the second cutting insert comprises a bottom surface opposite atop surface, wherein a side surface connects the top and bottomsurfaces,

wherein a mid-plane extends mid-way between the top and bottom surfaces,

wherein the top surface of the second cutting insert is facing away fromthe coupling portion,

wherein a longitudinal center axis of the coupling portion defines atool rotational axis,

wherein the intermediate portion extending along a longitudinal centeraxis thereof,

wherein in a top view, a greatest distance between the first and secondcutting inserts is greater than a width of the front end of the toolbody, where said width of the front end of the tool body is measuredperpendicular to said greatest distance between the first and secondcutting inserts,

wherein a length of the intermediate portion, measured along thelongitudinal center axis, is greater than the greatest distance betweenthe first and second cutting inserts.

By such a turning tool, the machine utilization may be further improved.

By such a turning tool, complex shapes can be machined more efficiently.

The turning tool is suitable for use in the above defined turningmethod.

The first and second cutting inserts are preferably made from a wearresistant material suitable for metal cutting, such as e.g. cementedcarbide.

The coupling portion and the intermediate portion are preferablypermanently connected, preferably from a piece of steel, and jointlyform a tool body.

The tool body extends between the coupling portion, arranged to beconnected directly or indirectly to a machine interface of a CNC-lathe,and a front end facing away from the coupling portion.

The front end of the tool body comprises the first insert seat for thefirst cutting insert and the second insert seat for the second cuttinginsert.

The first cutting insert comprises a bottom surface arranged to functionas a seating surface and an opposite a top surface arranged to comprisea rake face. The top surface of the first cutting insert is facing awayfrom the coupling portion.

The top surface preferably comprises chip breaking means, preferably inthe form of one or more protrusions and/or depressions. The bottomsurface preferably comprises anti-rotation means in the form of one ormore protrusions and/or depressions, for co-operation with anti-rotationmeans in the first insert seat. Alternatively, the bottom surface may bewithout anti-rotation means. For example, the bottom surface may be flator substantially flat. In such a case, the side surface, which connectsthe top and bottom surfaces, function as a seating surface or a contactsurface, i.e. the side surface is in contact with a surface of the firstinsert seat.

One or more cutting edges are formed in the intersection between the topsurface and the side surface. In a top view, the top surface may haveany shape.

The first and second cutting insert may comprise respective first andsecond cutting edges, connected by a respective nose cutting edge. In atop view, the front end of the tool body is inside lines coinciding withthe respective first and second cutting edges of the first and secondcutting inserts. By such a turning tool, more complex shapes can bemachined.

The first cutting insert comprise a cutting edge, arranged to be asurface generating cutting edge, which in top view is convexly curved,such as a preferably in the form of a circular arc or a circle having aradius of curvature of 0.15-30 mm, even more preferably 0.3-25 mm.

A mid-plane extends mid-way between the top and bottom surfaces and ispreferably arranged perpendicular to or substantially perpendicular tothe longitudinal center axis of the intermediate portion.

Preferably, a hole, i.e. a through hole, for a clamping screw preferablyopens in the top and bottom surfaces.

The second cutting insert may be arranged, i.e. shaped, in acorresponding manner as the first cutting insert. Alternatively, thesecond cutting insert may have a shape which is different to the firstcutting insert.

The top surface of the second cutting insert is facing away from thecoupling portion.

In a top view, the cutting first and second cutting inserts arepreferably completely inside an outer peripheral surface of the couplingportion. The second cutting insert is positioned in the second insertseat.

The first and the second cutting inserts are detachably clamped ormounted in respective insert seats by clamping means, preferably in theform of a clamping screw.

The first and second insert seats are spaced apart and are preferablylocated on opposite sides relative to the longitudinal center axis ofthe intermediate portion. The first and second cutting inserts each formfree ends of the turning tool. In other words, each of the first andsecond cutting insert comprises surface generating convex cutting edgeswhich form free ends of the turning tool.

A mid-plane of the second cutting insert, which extends mid-way betweenthe top and bottom surfaces of the second cutting insert is preferableco-planar with a corresponding mid-plane of the first cutting insert.

A longitudinal center axis of the coupling portion defines a toolrotational axis, and is preferably co-linear, alternatively parallel tothe longitudinal center axis of the intermediate portion.

In a top view, a greatest distance between the first and second cuttinginserts, more specifically portions of the first and second cuttinginserts which are arranged to function as surface generating portions orcutting edges, is greater than a width of the front end of the toolbody, where said width of the front end of the tool body is measuredperpendicular to said greatest distance between the first and secondcutting inserts.

In other words, the front end, and the intermediate portion, iselongated when seen in a front view.

The intermediate portion has a length or distance along the longitudinalcenter axis. Cross sections of the intermediate portion are preferablyuniform or substantially uniform from the front end of the tool body upto at least 50%, even more preferably up to at least 70%, of saiddistance.

Said length or distance of the intermediate portion is greater, evenmore preferably 50-300% greater, than a greatest distance between thefirst and second cutting inserts.

DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in more detail by adescription of different embodiments of the invention and by referenceto the accompanying drawings.

FIG. 1 is a perspective view of a tool body which is part of a firstturning tool.

FIG. 2 is a perspective view of the first turning tool.

FIG. 3 is a perspective view of the insert seat of the tool body in FIG.1.

FIG. 4 is a side view of the turning tool in FIG. 2.

FIG. 5 is a further side view of the turning tool in FIG. 2.

FIG. 6 is a side view of a second turning tool.

FIG. 7 is a perspective view of the turning tool in FIG. 6.

FIG. 8 is a top view of the turning tool in FIG. 6.

FIG. 9 is a perspective view of a third turning tool.

FIG. 10 is a side view of the turning tool in FIG. 9.

FIG. 11 is a perspective view of the tool body in FIG. 9.

FIG. 12 is a perspective view of the insert seat of the tool body inFIG. 11

FIG. 13 is a perspective view of the cutting insert in FIG. 9.

FIG. 14 is a side view of the cutting insert in FIG. 13.

FIG. 15 is a top view of the cutting insert in FIG. 13.

FIG. 16 is a further perspective view of the cutting insert in FIG. 13.

FIG. 17 is a side view of a fourth turning tool.

FIG. 18 is a further side view of the turning tool in FIG. 17.

FIG. 19 is a perspective view of the turning tool in FIG. 17.

FIG. 20 is a top view of the turning tool in FIG. 17.

FIG. 21 is a side view of a first turning method using the turning toolin FIG. 9.

FIG. 22 is a side view of modified first turning method using theturning tool in FIG. 9.

FIG. 23 is a second side view of FIG. 21.

FIG. 24 is a perspective view of the turning tool and metal work pieceshown in FIG. 21.

FIG. 25 is a side view of a second turning method using the turning toolin FIG. 17.

FIG. 26 is a further side view of the second turning method using theturning tool in FIG. 17.

FIG. 27 is a side view of a third turning method using the turning toolin FIG. 6.

FIGS. 28-37 are illustrations of a fourth turning method.

FIG. 38 is showing FIGS. 29 and 30 combined.

FIG. 39 is an enlarged view of a portion of FIG. 38.

FIGS. 40-49 are illustrations of a fifth turning method.

FIG. 50 is a sixth turning method.

FIG. 51 is a seventh turning method.

FIG. 52 is an eight turning method using the fifth turning tool.

FIGS. 53-58 are illustrations of a ninth turning method using the fifthturning tool.

FIG. 59 is a perspective view of a fifth turning tool.

FIG. 60 is a side view of the turning tool shown in FIG. 59.

FIG. 61 is a further side view of the turning tool shown in FIG. 59.

FIG. 62 is a top view of the turning tool shown in FIG. 59.

All turning tool and cutting insert figures have been drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention will now be described more in detail, and examples ofturning tools which can be used to perform the method according to theinvention are described. Five turning tools are explained in moredetail. Such turning tools have been found to be particularly suitablefor performing the above described turning method. Nine turning methodswill be describe, some in general terms, some in more detail. Alldescribed turning tools can be used for any of the described turningmethods.

Reference is made to FIGS. 1-5 which shows a first turning tool 1comprising a tool body 3 and a first cutting insert 2. The tool body 3is shown in FIG. 1 without the cutting insert 2. The turning toolcomprises an insert seat 6 which is shown in FIG. 3. The turning tool 1is a turning tool, comprising a coupling portion 4, an intermediateportion 5 and a cutting portion 2. The coupling portion 4 and theintermediate portion 5 are permanently connected and jointly form a toolbody 3 made from steel. The first cutting insert 2 is made from cementedcarbide. The first turning tool 1 comprises only one cutting insert. Thecoupling portion 4 is suitable to be connected to a rotatable machineinterface (not shown), such as a machine spindle. The coupling portion 4comprise a substantially conical or tapered portion 39 and a ring-shapedportion 40 in accordance to ISO 26623-1:2014. Alternatively, other quickshape coupling portions may be used.

A front end 20 or a forward end of the tool body 3 is defined by a firstinsert seat 6 for the first cutting insert 2. The first cutting insert 2is detachably clamped in the first insert seat 6 by clamping means 14,said clamping means being in the form of a clamping screw 14.

The first cutting insert 2 comprises a bottom surface 8 opposite a topsurface 7. A side surface 9 connects the top and bottom surfaces 7, 8.As seen in FIG. 4, a mid-plane M1 extends mid-way between the top andbottom surfaces 7, 8.

The intermediate portion 5 extends between the coupling portion 4 andthe cutting portion 2.

A longitudinal center axis of the coupling portion 4 defines a toolrotational axis R1.

The intermediate portion 5 extends along a longitudinal center axis A1thereof.

For the first turning tool 1, the longitudinal center axis A1 isco-linear or co-axial with the tool rotational axis R1, as seen in FIGS.2, 4 and 5.

The mid-plane M1 is perpendicular to the longitudinal center axis A1 ofthe intermediate portion 5, and perpendicular to the rotational axis R1.

The top surface 7 of the first cutting insert 2 is facing away from thecoupling portion 4. The top surface 7 is non-planar, and comprises chipbreaking means or chip breakers, in the form of protrusions.

The first cutting insert 2 comprises a first and a second nose portion10, 10′, which each form free ends of the turning tool 1.

The first nose portion 10 comprises a first cutting edge 11, a secondcutting edge 12, both straight in a top view, and a convex nose cuttingedge 13 connecting the first and second cutting edges 11, 12. The convexnose cutting edge 13 is convex in a top view. The nose cutting edge 13is in top view convexly curved having a radius of curvature of 0.15-1.3mm. Although a top view of the turning tool according to the firstembodiment is not shown, a top view of the first cutting insert 2according to the first embodiment is shown in FIG. 8 which show anidentical cutting insert.

According to the first embodiment, the radius of curvature is 0.4 mm.The first and second cutting edges 11, 12 forms a nose angle which is35°.

In a top view, the first and second nose portions 10, 10′ form an angleof 180° relative to each other measured around the longitudinal centeraxis A1 of the intermediate portion 5.

The first cutting insert 2 is 180° symmetric in top and bottom views.The first cutting insert is in a top view parallelogram-shaped.

As seen in FIG. 3, the first insert seat 6 comprises first insert seatrotational locking means comprising ridges 23-26, where two ridges 23,26 are co-linear, and two ridges 24, 25 are parallel.

The first cutting insert 2 comprises first cutting insert rotationallocking means in the form of grooves (not shown), formed in the bottomsurface 8, co-operating with the first insert seat rotational lockingmeans 23-26. The first cutting insert 2 comprises a hole for theclamping screw 14. Said hole 13 intersects the top and bottom surfaces8, 9, and a center axis thereof defines a first cutting insert centeraxis co-linear with the rotational axis R1 and the longitudinal centeraxis A1.

The turning tool 1 comprises a coolant channel formed in the tool body 3and extending between the coupling portion 4 and a nozzle 28. Saidnozzle 28 is formed in the intermediate portion 5, and the coolantchannel and the nozzle 28 are arranged to direct a coolant fluid towardsthe first and second nose portions 10, 10′.

Reference is now made to FIGS. 9-16 showing a third turning tool 1,comprising a first cutting insert 2. The principal differences comparedto the first turning tool relates to the designs of the first cuttinginsert 2 and the insert seat 6.

In a top view as seen in FIG. 15, a first extension line 21 co-linearwith the first cutting edge 11 and a second extension line 22 co-linearwith the second cutting edge 12 extends on opposite sides relative tothe first cutting insert center axis A2, which axis is co-linear withthe rotational axis R1 and the longitudinal center axis A1 when thecutting insert 2 is mounted in the insert seat 6. The previous sentenceis true also for the turning tool 1 according to the first embodiment.

The first cutting insert 2 comprises three nose portions 10, 10′, 10″.The first cutting insert 2 is 120° symmetrical in top and bottom views.

In a top view as seen in FIG. 15 the first and second cutting edges 11,12 forms a nose angle a which is 35°.

As seen in FIG. 12, the first insert seat 6 comprises first insert seatrotational locking means comprising ridges 23-25, where said ridges23-25 extend radially in relation to a hole 32 for the clamping screw 14formed in the first insert seat 6.

The first cutting insert 2 comprises first cutting insert rotationallocking means comprises grooves 16-18 formed in the bottom surface 8,co-operating with the first insert seat rotational locking means 23-26.

Reference is now made to FIG. 17-20, showing a fourth turning tool 1.The fourth turning tool 1 principally differs from the first turningtool in that the turning tool 1 comprises a second and a third cuttinginsert 29, 30, clamped our mounted in a second and third insert seat,respectively. Said second and third insert seats are formed in theintermediate portion 5 of the tool body 3 longitudinally between andspaced apart from the first cutting insert 2 and the coupling portion 4.

The second cutting insert 29 and the third cutting insert 30 is eachdifferent in shape in a top view compared to the first cutting insert 2.The third cutting insert 30 is a threading insert.

The second and third cutting insert 29, 30 each comprises nose portions,where each of said nose portions comprises a set of cutting edges.

Compared to the first cutting insert 2, the second and third cuttinginserts 29, 30 are placed at a greater distance from the longitudinalcenter axis A1 of the intermediate portion 5.

In a top view as seen in FIG. 20, the second and third cutting inserts29, 30 forms equally large angles or substantially equally large anglesin relation to the first and second nose portions. In FIG. 20, the firstcutting insert comprise two nose portions 10, 10′ which are placed at 6o′clock and at 12 o'clock, respectively. The second cutting insert 29 isplaced at 9 o'clock, and the third cutting insert 30 is placed at 9o'clock, where the time references refers to an analogue 12-hour watchand relates to the relative position in relation to the longitudinalcenter axis A1. By such a turning tool, the clearance is furtherimproved.

As seen in FIG. 17, the second and third cutting inserts 29, 30 arepositioned longitudinally at equal distances or substantially equaldistances from the clamping portion 4.

Reference is now made to FIG. 6-8, showing a second turning tool 1. Thesecond turning tool 1 principally differs from the first turning tool inthat for the second turning tool 1, the longitudinal center axis A1 isparallel to and spaced apart from the tool rotational axis R1, and theconvex nose cutting edge 13 of the first nose portion 10 intersects orsubstantially intersects the tool rotational axis R1. In other words,the intermediate portion 5 is offset in relation to the tool rotationalaxis R1. A mid-point of the convex nose cutting edge 13 of the firstnose portion 10 is positioned less than or equal to 0.5 mm from the toolrotational axis R1.

In other aspects, the second turning tool 1 is identical to or similarto the first turning tool. For example, in a top view as seen in FIG. 8a first extension line 21 co-linear with the first cutting edge 11 and asecond extension line 22 co-linear with the second cutting edge 12extends on opposite sides relative to the longitudinal center axis A1 ofthe intermediate portion 5.

In accordance with the first, third and fourth embodiment, in a top viewas seen in FIG. 8, the intermediate portion 5 and the first cuttinginsert 2 is inside an outer boundary line of the coupling portion 4.

Attention is now drawn to FIG. 21, showing in a side view the relativeposition and orientation of a metal work piece 31 and the third turningtool 1 when performing a first turning method. Alternatively, any otherof the above described turning tools can be used. The turning tool 1comprises a coupling portion 4 clamped to a machine interface 40 of aCNC-lathe (not shown), an intermediate portion 5 and a cutting portion 2in the form of a cutting insert. The CNC-lathe (not shown) can beinstructed to perform the turning method by instructions in a computerprogram, a computer readable medium or a data stream. A longitudinalcenter axis of the coupling portion 4 defines a tool rotational axis R1.The intermediate portion 5 extends along a longitudinal center axis A1thereof. The cutting portion 2 comprises a top surface facing away fromthe coupling portion 4.

The metal work piece 31 rotates around a work piece rotational axis R2in a clock-wise direction in FIG. 21.

The tool rotational axis R1 is perpendicular to the work piecerotational axis R2. The tool rotational axis R1 is arranged such that atangent line of the metal work piece 31 at the point of contact with theconvex nose cutting edge 13 intersect the coupling portion 4. Thetangential cutting force is directed towards the machine interface 40.The tool rotational axis R1 is spaced apart by a distance from aperipheral surface of the metal work piece 31. The tool rotational axisR1 is parallel to said tangent line.

Attention is now drawn to FIG. 22, showing the relative position andorientation of a metal work piece 31 and the third turning tool 1 whenperforming an alternative of the first turning method. The arrangementin FIG. 22 differs from FIG. 21 only in that the tool rotational axis R1is not parallel to said tangent line, but forms an angle less than orequal to 10° in relation to said tangent line.

Attention is now drawn to FIG. 23, showing a side view of the centerposition of the cutting insert 2, including the turning tool 1, duringmachining of a predetermined feature in the form of an external pocketor groove 52. The machining of the external groove 52 includes anon-linear, i.e. curved, first pass such that the first cutting edge isactive and such that the second cutting edge is inactive, such that afirst machined surface is generated by the convex nose cutting edge, andsuch that during at least a portion of the first pass, an entering angleand an angle which the first cutting edge forms in relation to the workpiece rotational axis R2 simultaneously varies. The machining of theexternal groove includes a non-linear, i.e. curved, second pass wherethe second cutting edge is active, and the first cutting edge isinactive, and wherein at least a portion of the first machined surfaceis machined during the second pass, thereby generating a second machinedsurface by the convex nose cutting edge. Said first pass is generallytowards the left-hand side and said second pass is generally towards theright-hand side in FIG. 23.

Attention is now drawn to FIG. 24, showing a perspective view of thearrangement shown in FIG. 21. The metal work piece 31 shown iscylindrical and comprises a lateral surface 31, i.e. a surface facingaway from the work piece rotational axis R2, and a base surface 42, i.e.a surface facing in a direction parallel to the work piece rotationalaxis R2. The metal work piece 31 comprises a second base surface, facingaway from the viewer. In the first turning method described above,machining is made in a lateral surface 41 of a metal work piece 31. Inthe third turning method shown in FIG. 27, machining is made in a basesurface 42 of a metal work piece 31.

Attention is now drawn to FIGS. 25 and 26, showing a second turningmethod using the fourth turning tool 1. The method includes using thefirst cutting insert 2, where the fourth turning tool 1 is in a positionrelative to the metal work piece 31 as shown in FIG. 25. The secondturning method comprises the step of machining using the first turninginsert 2 according to any of the above or below described turningmethods. The second turning method further comprises the steps ofwithdrawing the turning tool 1 from the metal work piece 31 and movingthe turning tool 1 in a forward direction along the tool rotational axisR1 to the position shown in FIG. 26. The method further comprises thestep of rotating the turning tool 1 around the tool rotational axis R1by a predetermined angle, such that the second cutting insert 29 is inan active position. Said predetermined angle is within the range of80°-100°.

Reference is now made to FIG. 27, showing a turning method using thesecond turning tool 1, although any of the above or below describedturning tools may be used. A metal work piece 31 is provided, whichrotates around a work piece rotational axis R2. The tool rotational axisR1 is perpendicular to the work piece rotational axis R2. The machiningor turning method is made at a base surface or end face of the metalwork piece 31.

The tool rotational axis R1 is perpendicular to the work piecerotational axis R2. In the example, both the work piece rotational axisR2 and the tool rotational axis R1 is in a horizontal position. Onepossible alternative is to arrange both the work piece rotational axisR2 and the tool rotational axis R1 in a vertical position.

The cutting insert 2 comprises first and second nose portions 10, 10′.In the method in FIG. 27, the second nose portion 10′ is in an activeposition. The method can alternatively be performed where the first noseportion 10 is in an active position. In such case, the turning tool 1 is180° rotated around the tool rotational axis R1.

The method comprises the step of making a first pass 36 by moving theturning tool such that the first cutting edge 11′ is active, such thatthe second cutting edge 12′ is inactive, and such that a machinedsurface is formed by the nose cutting edge 13′.

The method comprises the step of making a second pass 37 by moving theturning tool such that the first cutting edge 11′ is inactive, such thatthe second cutting edge 12′ is active, and such that at least a portionof a machined surface from the first pass 37 is machined.

During the first pass the turning tool rotates in a first direction,counter-clockwise in FIG. 34, around the tool rotational axis R1.

During the second pass 37 the turning tool rotates in a second directionaround the tool rotational axis, where said second direction, clock-wisein FIG. 27, is opposite to said first direction.

During the first pass 36 the turning tool is moved along non-linear orcurved path. The first pass comprises a radial component 34 which isperpendicular to and towards the work piece rotational axis R2,downwards in FIG. 27.

During the second pass 37 the turning tool is moved along a path whichis non-linear or curved. The second pass comprises a radial component 35which is perpendicular to and away from the work piece rotational axisR2, upwards in FIG. 27, i.e. opposite to the radial component 34 of thefirst pass.

During the at least a portion of said first and second passes 36, 37,respectively, an entering angle and an angle which the first cuttingedge forms in relation to the work piece rotational axis R2simultaneously varies.

After the first pass 36 but prior to the second pass 37, the turningtool is withdrawn from the metal work piece 31.

Attention is now drawn to FIGS. 28-37. A cutting portion 2 in the formof a cutting insert 2 is shown. The remaining parts of the turning toolis not shown. A turning tool as described as the first, second, fourthor fifth turning tool may be used. FIGS. 28-37 show a sequence or stepsof a turning method, which together form a first pass. The figures arein chronological order. The cutting insert 2 is in FIGS. 28-31 movedupwards in the figures, i.e. towards the work piece rotational axis R2,i.e. a radial motion. The cutting insert 2 is in FIGS. 33-37 moved tothe right-hand side in the figures, i.e. substantially parallel to thework piece rotational axis R2, i.e. a longitudinal motion. FIG. 32 showsthe end of the radial motion, and the start of the longitudinal motion.The machining sequence illustrate a non-linear first pass where a firstmachined surface 38 is generated by the convex nose cutting edge 13 andwhere the first cutting edge 11 is active. The tool rotational axis (notshown) is directed or orientated towards the viewer, in other words, thetool rotational axis is perpendicular to or substantially perpendicularto the work piece rotational axis R2.

During the at least a portion of said first pass, an entering angle Kand an angle β which the first cutting edge forms in relation to thework piece rotational axis R2 simultaneously varies.

FIG. 38 show FIGS. 29 and 30 together, where FIG. 30 show the positionof the turning insert 2 in a position after the metal work piece hasmade one revolution around the rotational axis thereof from the turninginsert 2 position of FIG. 29. It can be seen that the entering angleincreases as the surface generating nose cutting edge 13 of the turninginsert 2 is moved forward. Between FIGS. 29 and 30, the movement of thesurface generating point 56 of the nose cutting edge 13 is linear,towards the rotational axis R2. The surface generating feed rate (perrevolution) is, at least approximately, the distance between therespective surface generating points 56 of the nose cutting edge 13 inFIGS. 29 and 30.

FIG. 39 show a section of FIG. 38. The chip area 44 is a representationof the area of material removed per revolution. The chip area 44 can atleast theoretically be understood as a cross section of a chip removedduring the turning process. As can be seen the chip area 44 is notuniform.

When the entering angle K varies, the maximum chip thickness h_(x) isthe maximum chip thickness measured along a line perpendicular to thefirst cutting edge 11.

When the entering angle K varies, the distance which the surfacegenerating point 56 of the nose cutting edge 13 moves per revolution canbe designated as the feed rate per revolution. Said feed rate perrevolution in this case, when the entering angle K varies, can bedesignated as the surface generating feed rate, and can be fined as thedistance which the surface generating point 56 of the nose cutting edgemoves per revolution of the metal work piece.

The maximum chip thickness 43 is preferably set to a constantpredetermined value or to be within a predetermined range during atleast a portion of the first pass 36.

Attention is now drawn to FIGS. 40-49. A cutting portion 2 in the formof a cutting insert 2 is shown. The remaining parts of the turning toolis not shown. A turning tool as described as the first, second, fourthor fifth turning tool may be used. FIGS. 28-37 show a sequence or stepsof a sequence of a turning method, which together form a first pass. Thefigures are in chronological order. The cutting insert 2 is in FIGS.40-41 and 48-49 is moved to the right-hand side in the figures, i.e.substantially parallel to the work piece rotational axis R2, i.e. alongitudinal motion. FIGS. 40-41 show a first longitudinal motion, andFIGS. 48-49 show a second longitudinal motion, at a smaller diameterthan the first longitudinal motion. FIGS. 42-48 show a profiling motionwhere the cutting insert is moved at an angle in relation to the workpiece rotational axis R2, towards the right-hand side in the figures andtowards the work piece rotational axis R2. FIG. 48 show the end positionof the cutting insert 2 in the profiling motion, which is also the startposition of the cutting insert 2 in the second longitudinal motion.

During the at least a portion of said first pass, an entering angle Kand an angle β which the first cutting edge forms in relation to thework piece rotational axis R2 simultaneously varies.

Attention is now drawn to FIG. 50. The fifth turning tool 1 is shown.The turning tool 1 comprises a first cutting insert 2, a second cuttinginsert 3, and a tool body 3. The tool body 3 comprises a couplingportion 4, an intermediate portion 5, and insert seats in which insertseats the first and second cutting inserts are mounted. A longitudinalcenter axis of the coupling portion 4 defines a tool rotational axis R1,around which tool rotational axis R1 the turning tool 1 is rotatable.Top surfaces of the respective first and second cutting inserts 2, 45are facing away from the coupling portion 4. A metal work piece 31 isrotatable around a work piece rotational axis R2. The tool rotationalaxis R1 is perpendicular to the work piece rotational axis R2. Theturning tool 1 is used to machine a predefined feature in the form of anexternal groove 52. The external groove 52 opens in a direction awayfrom the work piece rotational axis R2. The groove 52 is limited by afirst side wall 48, a second side wall 49, a bottom surface 47, a firstcorner surface 50 and a second corner surface 51. The first cornersurface 50 is connecting the bottom surface 47 and the first side wall48. The second corner surface 51 is connecting the bottom surface 47 andthe second side wall 49. The machining of the groove 52 includes asequence of non-linear passes, where a sequence of machined surfaces isgenerated by the nose cutting edge 13 of the first cutting insert 2. Thepasses of the machining sequence include machining alternatively inlongitudinally substantially opposite directions, in other wordsalternatively substantially towards the right-hand side, where the firstcutting edge 11 is active, and alternatively towards the left-hand side,where the second cutting edge 12 is active.

The machining sequence includes a first non-linear pass 36 where a firstmachined surface 38 is generated by the convex nose cutting edge 13, andwhere the first cutting edge 11 is active. The first non-linear pass 36is followed by a second non-linear pass 37 where a second machinedsurface 39 is generated by the nose cutting edge 13, and where thesecond cutting edge 12 is active.

Attention is now drawn to FIG. 51. An external groove 52 is machined bya turning tool (not shown) comprising a first cutting insert 2. Aturning tool as described as the first, second, fourth or fifth turningtool may be used. Multiple positions of the first cutting insert 2during a non-linear first pass is shown, where the first cutting insertis moved towards the right-hand side. The groove 52 is limited by afirst side wall 48, a second side wall 49, a bottom surface 47, a firstcorner surface 50 and a second corner surface 51. The first cornersurface 50 is connecting the bottom surface 47 and the first side wall48. The second corner surface 51 is connecting the bottom surface 47 andthe second side wall 49. The bottom surface 47 is a cylindrical surfaceconcentric with the work piece rotational axis R2.

During the non-linear first pass, the first cutting edge 11 is activeand the second cutting edge 12 is inactive. A first machined surface 38is generated by the convex nose cutting edge 13. During at least aportion of the first pass 36, an entering angle K and an angle β whichthe first cutting edge 11 forms in relation to the work piece rotationalaxis R2 simultaneously varies.

The turning method comprises the steps of setting a second cornersurface corner surface 51 entering angle K₂, a second corner surface 51exit entering angle K₃, a bottom surface 47 longitudinal exit enteringangle K₅, and an entering angle K₆ at the exit of the first cornersurface 50

The non-linear first pass may be such that the nose cutting edge 13and/or first cutting edge 11 goes into cut prior to the second cornersurface 51. In such a case, an entry entering angle is designated K_(i)(not shown). In a similar manner, the non-linear first pass may be suchthat the nose cutting edge 13 and/or first cutting edge 11 goes out ofcut after the first corner surface 50.

The corner entering angle K₂ is greater than the corner exit enteringangle K₃. The longitudinal exit entering angle K₅ is greater than thecorner exit entering angle K₃.

The corner entering angle K₂ is set to 60-120°, even more preferably80-110°. Preferably, the corner exit entering angle K₃ is set to 20-80°,even more preferably 25-45°. Preferably, the longitudinal exit enteringangle K₅ is set to 60-120°, even more preferably 80-110°.

K₆ is preferably set to 10-80°, even more preferably 25-45°.

During the first non-linear pass, the entering angle K is preferablycontinuously, i.e. without steps, i.e. step-less, varied during at leasta portion of the non-linear first pass. Alternatively, the enteringangle K is incrementally varied, preferably in steps of less than 2°.

During the first non-linear pass, the rotation of the turning toolaround a tool rotational axis is in one direction only, clock-wise whenseen as in FIG. 51, where a coupling portion is away from the viewer.

Attention is now drawn to FIG. 52. An external groove 52 is machined bythe fifth turning tool 1 comprising a first cutting insert 2 and asecond cutting insert 45. Multiple positions of the first turning tool 1during a non-linear first pass is shown, where the turning tool 1 ismoved towards the right-hand side. The groove 52 is limited by a firstside wall 48, a second side wall 49, a bottom surface 47, a first cornersurface 50 and a second corner surface 51. The first corner surface 50is connecting the bottom surface 47 and the first side wall 48. Thesecond corner surface 51 is connecting the bottom surface 47 and thesecond side wall 49. The bottom surface 47 is a cylindrical surfaceconcentric with the work piece rotational axis R2.

During the non-linear first pass, the first cutting edge 11 of the firstcutting insert 2 is active and the second cutting edge 12 is inactive.The second cutting insert 45 is inactive. A first machined surface 38 isgenerated by the convex nose cutting edge 13. The nose cutting edge 13is moved towards the first corner surface 50. During at least a portionof the first pass 36, an entering angle K and an angle β which the firstcutting edge 11 forms in relation to the work piece rotational axis R2simultaneously varies. The turning method comprises the step ofincreasing a speed of rotation of the turning tool 1 around the toolrotational axis (not shown) as a portion of the turning tool 1, spacedapart from the first cutting insert 2, reaches a predetermined distance46 from the first side wall 48. Thus, the risk of collision can bereduced. The entering angle K is increased during at least a portion ofthe first pass 36.

During the first non-linear pass, the rotation of the turning toolaround a tool rotational axis is in one direction only, clock-wise whenseen as in FIG. 51, where a coupling portion is away from the viewer.

Attention is now drawn to FIGS. 53-58. An external groove 52 is machinedby the fifth turning tool 1 comprising a first cutting insert 2 and asecond cutting insert 45. The positions of the first turning tool 1during a portion of a non-linear first pass is shown in chronologicalorder in FIGS. 53-56. The turning tool 1 is moved generally towards theright-hand side in FIGS. 53-56, followed by a general movement downwardsin FIGS. 56-58. The groove 52 is limited by a first side wall 48, asecond side wall 49, a bottom surface 47, a first corner surface 50 anda second corner surface 51. The first corner surface 50 is connectingthe bottom surface 47 and the first side wall 48. The second cornersurface 51 is connecting the bottom surface 47 and the second side wall49. The bottom surface 47 is a cylindrical surface concentric with thework piece rotational axis R2

During the non-linear first pass, the first cutting edge 11 of the firstcutting insert 2 is active and the second cutting edge 12 is inactive.The second cutting insert 45 is inactive. A first machined surface 38 isgenerated solely by the convex nose cutting edge 13. The nose cuttingedge 13 is moved towards the first corner surface 50. During at least aportion of the first pass 36, an entering angle K and an angle β whichthe first cutting edge 11 forms in relation to the work piece rotationalaxis R2 simultaneously varies. The turning method comprises the step ofincreasing a speed of rotation of the turning tool 1 around the toolrotational axis, co-linear with a longitudinal center axis A1 of anintermediate portion 5 of a tool body of the turning tool 1, as aportion of the turning tool 1, spaced apart from the first cuttinginsert 2, reaches a predetermined distance 46 from the first side wall48. Thus, the risk of collision can be reduced. The entering angle K isincreased during at least a portion of the first pass 36.

During the machining of the bottom surface 47, the entering angle K andthe angle β which the first cutting edge 11 forms in relation to thework piece rotational axis R2 have the same value. During the machiningof at least a portion of the first corner surface 50, as seen in FIG.56, said angles have different values.

Attention is now drawn to FIGS. 59-62, showing a fifth turning tool 1which is particularly suitable for any of the above described turningmethods. The fifth turning tool 1 comprises a tool body 3, a firstcutting insert 2 and a second cutting insert 45. The tool body 3comprises a coupling portion 4, an intermediate portion 5, a firstinsert seat 6 for the first cutting insert 2 and a second insert seatfor the second cutting insert 45. The tool body 3 extends between thecoupling portion 4 and a front end 20 of the tool body 3. The front endof the tool body 3 comprises the first insert seat 6 and the secondinsert seat. The first cutting insert 2 comprises a bottom surface 8opposite a top surface 7, and a side surface 9 which connects the topand bottom surfaces 7, 8. A mid-plane M1 extends mid-way between the topand bottom surfaces 7, 8. The top surface 7 of the first cutting insert2 is facing away from the coupling portion 4. The second cutting insert45 comprises a bottom surface 8′ opposite a top surface 7′, and a sidesurface 9′ which connects the top and bottom surfaces 7′, 8′. Amid-plane M1′ extends mid-way between the top and bottom surfaces 7′,8′. The top surface 7′ of the second cutting insert 45 is facing awayfrom the coupling portion 4. A longitudinal center axis of the couplingportion 4 defines a tool rotational axis R1. The intermediate portion 5extends along a longitudinal center axis A1 thereof. In a top view asseen in FIG. 62, a greatest distance 52 between the first and secondcutting inserts 2, 45 is greater than a width 53 of the front end 20 ofthe tool body 3, where said width 53 of the front end 20 of the toolbody 3 is measured perpendicular to said greatest distance 52 betweenthe first and second cutting inserts 2, 45. As seen in FIG. 61, a length54 of the intermediate portion 5, measured along the longitudinal centeraxis A1 is greater than the greatest distance 52 between the first andsecond cutting inserts 2, 45.

Each top surface 7, 7′ of the first and second cutting inserts 2, 45comprises chip breaking means or chip breakers, preferably in the formof one or more protrusions and/or depressions. In FIGS. 59-64, thecutting inserts both have a rhombic shape in a top view. However, thefirst and second cutting inserts does not have to have a correspondingshape. Further, in top view, the first and second inserts may have anyshape. The coupling portion 4 of the fifth turning tool 1, and of thesecond, third and fourth turning tool, is in accordance with thecoupling portion 4 of the first turning tool 1.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprises” and “comprising” and not preclude the presence of otherstructure, material, or acts. Similarly, though the use of terms such as“can” or “may” is intended to be open-ended and to reflect thatstructure, material, or acts are not necessary, the failure to use suchterms is not intended to reflect that structure, material, or acts areessential. To the extent that structure, material, or acts are presentlyconsidered to be essential, they are identified as such. Terms such as“upper”, “upwards”, “lower”, “top”, “bottom”, “forward”, “right”,“left”, “front” and “rear” refer to objects as shown in the currentdrawings and as perceived by the skilled person.

1. A turning method for a computerized numerical control lathecomprising the steps of: providing a turning tool including a cuttingportion, the cutting portion having a first nose portion, the first noseportion including a first cutting edge, a second cutting edge, and aconvex nose cutting edge connecting the first and second cutting edges,wherein the first and second cutting edges are straight or substantiallystraight in a top view; providing a metal work piece; rotating the metalwork piece around a work piece rotational axis; and making a first passsuch that the first cutting edge is active and the second cutting edgeis inactive, wherein a first machined surface is generated by the convexnose cutting edge, and such that during at least a portion of the firstpass, an entering angle and an angle, which the first cutting edge formsin relation to the work piece rotational axis, simultaneously varies. 2.The turning method according to claim 1, wherein the first pass is anon-linear first pass.
 3. The turning method according to claim 1,further comprising the step of, during at least a portion of the firstpass, increasing the entering angle and reducing a surface generatingfeed rate.
 4. The turning method according to claim 1, wherein theentering angle and the angle, which the first cutting edge forms inrelation to the work piece rotational axis, continuously varies.
 5. Theturning method according to claim 1, wherein the entering angle and theangle, which the first cutting edge forms in relation to the work piecerotational axis, varies by a rotation of the turning tool around a toolrotational axis, wherein the tool rotational axis is perpendicular to orsubstantially perpendicular to the work piece rotational axis.
 6. Theturning method according to claim 5, further comprising the step of,during at least a portion of the first pass, moving the tool rotationalaxis in relation to the work piece rotational axis.
 7. The turningmethod according to claim 1, further comprising the step of, during atleast a portion of the first pass, moving the turning tool towards thework piece rotational axis.
 8. The turning method according to claim 2,wherein the entering angle and the angle, which the first cutting edgeforms in relation to the work piece rotational axis, varies during anon-linear portion of the non-linear first pass.
 9. The turning methodaccording to claim 1, further comprising the step of setting a maximumchip thickness to a constant predetermined value or to be within apredetermined range during at least a portion of the first pass.
 10. Theturning method according to claim 2, wherein the first non-linear passincludes machining of a bottom surface of an external groove, whereinthe groove is limited by a first side wall, a second side wall, thebottom surface, a first corner surface and a second corner surface,wherein the first corner surface is connected to the bottom surface andthe first side wall, wherein the second corner surface is is connectedto the bottom surface and the second side wall, the method furthercomprising the steps of moving the nose cutting edge towards the firstcorner surface; and increasing a speed of rotation of the turning toolaround a tool rotational axis as a portion of the turning tool, spacedapart from the first cutting insert, reaches a predetermined distancefrom the first side wall.
 11. The turning method according to claim 1,further comprising the step of during, at least a portion of the firstpass, setting a chip area to be below a predetermined value or to bewithin a predetermined range.
 12. The turning method according to claim1, further comprising the step of setting the maximum chip width to apredetermined value or to a predetermined range during at least aportion of the first pass.
 13. The turning method according to claim 1,further comprising the step of making a second pass such that the secondcutting edge is active and the first cutting edge is inactive, whereinat least a portion of the first machined surface is machined during thesecond pass, thereby generating a second machined surface by the convexnose cutting edge.
 14. The turning method according to claim 1, whereinthe cutting portion is in the form of a cutting insert, wherein thecutting insert including a top surface, wherein in a top view an anglebetween the first cutting edge and a second cutting edge is less than90°, and wherein in the top view, the convex nose cutting edge has aradius of curvature which is 0.15-1.3 mm, wherein the turning toolincludes a tool body, the tool body having a coupling portion, anintermediate portion, and an insert seat, wherein the intermediateportion extends along a longitudinal center axis thereof, wherein thecutting insert is mounted in the insert seat, wherein the tool bodyextends between the coupling portion and a front end of the tool body,the front end of the tool body includes the insert seat, wherein the topsurface of the cutting insert is facing away from the coupling portion,wherein a longitudinal center axis of the coupling portion defines atool rotational axis, wherein the entering angle and the angle, whichthe first cutting edge forms in relation to the work piece rotationalaxis varies during the first pass as a result of a rotation of theturning tool around the tool rotational axis.
 15. The turning methodaccording to claim 14, wherein in the top view, the intermediate portionis at least 50% more elongated along a bisector formed between the firstand second cutting edges than along a line, which is perpendicular tothe bisector and intersects the longitudinal center axis of theintermediate portion.
 16. A computer program having computer executablecode, which when executed by a computer numerical control lathe causesthe computer numerical control lathe to perform the method according toclaim
 1. 17. An automated computer-implemented method for generatingcommands for controlling a computer numerically controlled machine tofabricate a feature from a metal workpiece rotatable around a work piecerotational axis thereof by means of a turning tool, wherein the turningtool includes a cutting portion, the cutting portion having a first noseportion, the first nose portion including a first cutting edge, a secondcutting edge, and a convex nose cutting edge connecting the first andsecond cutting edges, wherein the first and second cutting edges arestraight or substantially straight in a top view, the method comprisingthe step of: configuring a first pass, such that the first cutting edgeis active and the second cutting edge is inactive, such that a firstmachined surface is generated by the convex nose cutting edge, and suchthat during at least a portion of the first pass, an entering angle andan angle, which the first cutting edge forms in relation to the workpiece rotational axis, simultaneously varies.
 18. The automatedcomputer-implemented method according to claim 17, further comprisingthe step of setting a maximum chip thickness to a constant predeterminedvalue or to be within a predetermined range during at least a portion ofthe first pass.
 19. The automated computer-implemented method accordingclaim 17, wherein the feature is in a form of an external groove limitedby a bottom surface, first and second side walls, and first and secondcorner surfaces, wherein the first corner surface connects the bottomsurface and the first side wall, wherein the second corner surfaceconnects the bottom surface and the second side wall, and wherein thefirst pass is non-linear and includes the machining of the bottomsurface and the second corner surface, the method further comprising thesteps of setting a corner entering angle, a corner exit entering angle,and a longitudinal exit entering angle, and step-less or incrementallyvarying the entering angle between the corner entering angle and thecorner exit entering angle, and between the corner entering angle andthe longitudinal exit entering angle.
 20. A turning tool comprising: atool body; and a cutting portion, wherein the cutting portion includes afirst cutting insert and a second cutting insert, wherein the tool bodyincludes a coupling portion, an intermediate portion, a first insertseat for the first cutting insert and a second insert seat for thesecond cutting insert, wherein the tool body extends between thecoupling portion and a front end of the tool body, wherein a front endof the tool body includes the first insert seat and the second insertseat, the first cutting insert having a bottom surface opposite a topsurface, wherein a side surface connects the top and bottom surfaces,wherein a mid-plane extends mid-way between the top and bottom surfaces,wherein the top surface of the first cutting insert is facing away fromthe coupling portion, wherein the second cutting insert includes abottom surface opposite a top surface, wherein a side surface connectsthe top and bottom surfaces, wherein a mid-plane extends mid-way betweenthe top and bottom surfaces of the second cutting insert, wherein thetop surface of the second cutting insert is facing away from thecoupling portion, wherein a longitudinal center axis of the couplingportion defines a tool rotational axis, wherein the intermediate portionextends along a longitudinal center axis thereof, wherein in a top view,a greatest distance between the first and second cutting inserts isgreater than a width of the front end of the tool body, where said widthof the front end of the tool body is measured perpendicular to saidgreatest distance between the first and second cutting inserts, andwherein a length of the intermediate portion, measured along thelongitudinal center axis, is greater than the greatest distance betweenthe first and second cutting inserts.